The prior art electromotive tool has power supplied by connecting wire to a power supply. However, this is inconvenient and thus chargeable electromotive tool with batteries is design to improve the prior art defect.
The prior art chargeable electromotive tool includes a plug-in tool and a battery seat. A top of the tool has a transversal operation portion. One end of the portion is a clamp for clamping a tool head. Another end is downward extended with a longitudinal handle. A bottom of the hollow handle has an inserting end which extends with the operation portion for assembling the battery seat.
The interior of the seat body of the battery seat has a battery, a transformer, and a charging circuit. One end of the seat body is protruded with an inserting post for inserting into the handle. A side of the inserting post has a conductive sheet. When it is inserted into a tool, it will contact the electrode in the tool. Two sides of the seat of the battery seat have respective buckles. In assembly, the inserting post of the battery seat will be inserted into the handle of the tool. Then palms of the buckles at the inner side of the inserting end of the tool serve to fix  it. The battery seat further has a power hole for receiving a power wire. When external power is necessary, the power wire can be inserted into the power hole and a receptacle on the building. Then power will supply to the battery from the receptacle. If it is unnecessary to supply power from outside, the power wire can be pulled out from the hole.
When the electromotive tool is used, a switch at one side of a handle is pressed for actuating the motor. When it is desired to change the rotation speed of the electromotive motor, a switching key near an operation portion of the handle is used.
However, above said prior art has the following disadvantages.
When power is supplied to the prior art electromotive tool externally, the battery in the battery seat can not be charged. Moreover, the battery seat and the operation portion of the tool extend along the same direction. The battery seat is installed with a battery, a transformer, a charging circuit, etc. and thus the volume of the battery seat is slightly smaller than the operation portion. When the tool is operated along a wall or a box body, no bad effect is induced, but when it is used in a concave portion and protrusions are at a periphery of the concave portion, the battery seat is easy to touch the protrusion so that it cannot be operated.
In the prior art, the battery seat is installed with a transformer. Since cores and windings are installed in the battery seat so that the weight and volume are larger. Since the electromotive tool is held by one hand and thus it is heavy, the user cannot hold it easily for operation. Thus efficiency and quality of the work are reduced. Or the hand of the user will feel ache. 
In the prior art electromotive tool, when the power wire is inserted into a power supply receptacle for supplying power externally. No sliding preventing structure is installed at the connection of the power wire and the electromotive tool. Thereby, it is easily dropped downward so as to interrupt the power. This is troublesome to the user.
In another prior art, the power wire and charging circuit are externally arranged for reducing the volume and weight of the battery seat so that when the power supply of the electromotive tool is mainly from the battery seat, the operation will not be interrupted by the heavy battery seat. However, this kind of prior art still has the following disadvantages.
The cost is high due to the independent charger and the manufacturing process is increased. Thereby, the cost is high. Thereby, the separated charger easily loses due to the disorder work place. Thereby, one more charger is necessary. This is a trouble to the users.
Thereby, in charging, the charger is connected to the battery seat so that the electromotive motor cannot work.